An American sexual orientation think-tank has released a report that reveals a “gay demographic explosion” in some of America’s most conservative regions.

The Williams Institute for Sexual Orientation Law and Public Policy at UCLA released the report yesterday.

The report used data from the 1990 and 2000 censuses and the US Census Bureau’s American Community Survey (ACS) from 2002 to 2006.

It was found that the number of same-sex couples in the United States has quadrupled since 1990, about 21 times higher than increase of the population as a whole.

The biggest growth came in regions the study termed “Southern,” “Midwest” and “Mountain,” including Alabama, Kentucky, Tennessee, Arizona and Utah.

Researchers used voting history to work out each region’s level of acceptance.

Places where George Bush Senior’s support was higher than the national average in the 1992 presidential election were deemed “conservative,” while those places where Bill Clinton’s support was above his national vote average in 1992 were deemed socially liberal.

The conservative regions all showed above-average growth in the numbers of same-sex couples since 1990, while the liberal regions all showed below-average growth.

Similarly, state recognition of same-sex unions was found to be inversely related to the rate of migration.

States that legislated same-sex civil unions or marriage between 2000 and 2006 showed a below-average increase (23 percent, compared to the national rate of 31 percent).

States where same-sex marriage was prohibited during those years experienced an above-average (37 per cent) increase, the states where marriage bans were enacted via voter referendum showing the highest increase of all (41 per cent).

The researchers put the increase down to greater acceptance of LGBT couples nationwide, more LGBT people choosing to couple and co-habit, and more couples moving to the suburbs, in migration patterns that differ from the nation as a whole.

Gary Gates, senior research fellow at the Williams Institute and author of the study, said: “Clearly, more same-sex couples are willing to openly identify themselves as such on government surveys.

“A combination of growing social acceptance and migration to the South and West means that same-sex couples are becoming increasingly visible in the most politically and socially conservative parts of the country.”

Gates believes his study could contain clues to the 2008 elections.

“It may very well be that these changes in the number of same-sex couples offer a ‘leading indicator’ to assess which historically conservative states are destined to become more ‘purple’ in upcoming elections.

“If so, keep an eye on Utah. Salt Lake City has passed legislation to formally recognise same-sex couples and Brigham Young University no longer considers being gay to be a violation of its honour code.

“Perhaps most notable, the state now has three openly gay officials in its state legislature. That’s one more than in the U.S. Congress.”

The study found that Utah is the biggest-moving state, leaping from 38th place for numbers of same-sex couples in 1990 to 14th place in 2006.

Other big movers included Delaware, which went from 33rd to 12th place, and New Mexico, which went from 16th to 2nd.

Since 2000, Vermont has had the highest number of same-sex households per thousand households.

Three of America’s 50 largest cities showed decreases in same-sex couples from 2000 to 2006: Atlanta, Philadelphia and Detroit.

Surrounding counties showed gains, which supports Gates’ theory that same-sex couples are moving to the suburbs.

The full report can be viewed at here.